It is probably one of the more common explanations offered by fans, sportswriters and commentators alike when trying to comprehend an athletes' decline in athletic performance -- 'stress.'
It was not uncommon this past year to hear the dreaded 'S' word attached to various athletes on different occasions, with perhaps the two biggest names being Lebron James and his disappointing performance in the NBA finals, and Tiger Woods whose PGA ranking has plummeted since the scandal of his affair and subsequent divorce.
Everyone knows that stress can have a negative impact on performance. But what exactly does this mean? In other words, how exactly could psychological stress affect athletic performance?
Let's take a closer look by examining the science of stress, and using Tiger Woods as a hypothetical case example.
By definition, stress is a reaction by the body and brain to meet the demands of some challenge or threat. Let's start with the effects of stress on the brain. Stress hormones such as cortisol have the ability to cross the blood-brain barrier and impair these important cognitive processes. Consequently, high levels of stress can negatively affect most aspects of human cognition; the key ones being attention, memory and decision-making.
There are two types of attention: external and internal. External attention refers to focusing on things outside of our bodies, whereas internal attention refers to focusing on internal psychological and physiological experiences (e.g. heart rate; thoughts). It is possible for both forms of attention to be active while trying to complete a task.
For example, you can carry on a conversation with someone (requiring external attention) while thinking of something unrelated (internal attention). Thus, we can come up with a ratio that describes the distribution of attention at any given time. If you're devoting 80 per cent outwardly and 20 per cent inwardly, the conversation should be fine. But if most of your attention is directed inwardly, you're not going to be a pleasant person to talk with.
External attention is important for things like visual perception, as it is difficult to accurately perceive something if your brain is not paying sufficient attention to it.
Accurate perception and the ability to focus one's attention are obviously key to the game of golf. Once stress starts to interfere with attention, which subsequently affects perception, the results can be terrible for performance.
If Tiger Woods' capacity for external attention has been reduced by say 10 per cent (due to stress), what effect would that have on his score across an entire tournament?
Stress can also have a particularly negative effect on working memory. Working memory is what we use when we must consider multiple pieces of information at once (e.g. decision-making).
In golf for example, while contemplating your strategy for how best to play a particular hole, you will simultaneously need to hold one or more pieces of information in mind (e.g. current wind speed, hole position) while making a particular decision (e.g. club selection).
In many ways, the brain is like a computer. If memory capacity is low or impaired, performance will be slower, less efficient and there will less information that can be processed at a given time. There is also a greater risk of errors in decision making if the brain cannot process all the necessary information.
With someone like Tiger Woods, it is unlikely the case that he is struggling to process golf information. He has played the game his whole life and things that are well-learned are less affected by stress. Therefore, his ability to process information is still going to be greater than most players' ability. However, this does not mean that his working memory and decision making are completely intact. As most golfers know (myself painfully included), it only takes one or two relatively poor decisions to ruin a golf score.
In addition to problems with cognitive processes like attention and memory, stress also tends to be accompanied by increases in worry and other forms of thought (e.g. rumination; analytic thinking). Returning to the computer analogy, these types of thoughts can act like multiple software programs running simultaneously and slowing things down.
To show how stress might interfere with the mental side of a golf performance, I'll use a concrete example that most golfers can understand and appreciate: putting.
While on the putting green, golfers must make use of multiple cognitive processes using multiple pieces of information in order to decide how to make their putt. It starts with attention and perception. The more distracted you are with inward focus, the more difficult it will be to focus externally on the green.
Visual perception is very important. You must be able to see subtle shifts in slope to find the true putting line.
Also, while trying to focus externally, it will be necessary to hold certain pieces of information in mind (e.g wind; previous experiences on this green; what your caddy is saying) while making a decision. This whole process of thinking, perceiving and evaluating requires processing capacity in the brain. The more stress in the background of one's life, the less processing capacity available at a given time.
Furthermore, this whole process requires some degree of patience -- unfortunately, impulsivity can increase under high stress loads as well.
As you can see, stress can make the mental side of the game more difficult.
Now, let's examine the physical effects of stress. Stress is often accompanied by physical symptoms. One of the most common physical symptom of stress is increased muscle tension, which can obviously interfere with motor functions like swinging a club.
Also, stress can interfere with both sleep quality and quantity. The interaction of muscle tension and troubled sleep often produces another physical symptom of stress -- fatigue. Stress also affects immune functioning, making people more susceptible to illnesses from viruses and bacteria, and can also have a negative effect on tissue repair. Indeed, recovery from injuries, including minor muscle tears, can be slowed by stress' negative impact on the body.
As you can see, stress has the potential seriously interfere with performance -- not only in sports, but in other domains as well (e.g. regular careers).
As Tiger Woods prepares to return to the world of professional golf, my advice to him and all professional athletes is this: if you think stress or some other mental health issue (e.g. anxiety) is impairing your performance, consider finding a good psychologist.